1. Chapter 4: Tissues, Part 1
Tissue = A collection of cells that perform related functions,
and are similar in structure, or a mass of like cells
Histology = The study of tissues
The Four Primary Tissue Types
Epithelial
Connective
Muscular
Nervous
Developed by
John Gallagher, MS, DVM

2. Epithelial Tissue
1. Epithelium / -a = cell layer (barrier)
 Epi = on or upon
 Protection: covering or lining—inside and out
 Permeability control: selective secretion and
absorption
 Sensation: touch receptors etc. and neuroepithelium
of special senses
2. Glands = secretory structure
 Specialized secretions
 Saliva, hormones, many others
•The Four Primary Tissue Types
Epithelial
Connective
Muscular
Nervous

3. A Concept Map
Epithelial
tissues
Squamous Columnar Cuboidal
Simple Stratified Simple Simple
Keratinized Pseudostratified Stratified
Nonkeratinized Transitional

4. Structural Characteristics of
Epithelia p 69
apical
Cellularity (little to no IC
Space)
Cell to cell contacts
Polarity (sometimes)
basal
Basement Membrane
Support by connective tissue
BM Avascular (esp. epidermis)
Regeneration/repair

5. Polarity of (some) Epithelial Cells

6. Classification of Epithelia
The function of the epithelium determines
which type.
Typically classified according to
1. Number of cell layers
Simple vs. Stratified
2. Shape of cell
Squamous, cuboidal, columnar

7. Simple Squamous Epithelium
Location:
 Lining of ventral body
cavities, e.g.
peritoneum
 Lining of blood
vessels (endothelium)
 Alveoli of lung
 Bowman’s Capsule

8. Function of Simple Squamous E.
 Friction reduction (cavity lining)
 Blood vessel permeability control
(capillaries and Bowman’s capsule)
 Gas absorption and secretion (lung)
 Not protective—only one cell thick

9. Lung

10. Simple Cuboidal Epithelium
 Function:
 Secretion
 Absorption
 Location: Lining of ducts
 e.g., kidney tubules
 Glands (salivary, pancreas, thyroid)

11. Kidney tubule
Thyroid Follicle

12. Simple Columnar Epithelium
 The “classic” epithelium
 Function:
 Secretion
 Absorption
 Location:
 GI tract
 Many excretory ducts
 Cilia (uterine tube)
 Microvilli (small intestine)

13. Pseudostratified Ciliated Columnar
Epithelium
 Function:
Mucociliary Blanket
 Mixture of cell types  nuclei
located at various distances from
surface. Yet: all cells contact BM
 Location:
Ducts of Respiratory tract
 i.e., trachea and bronchi

15. Stratified Squamous Epithelium
 Function
Protection against abrasion, pathogens,
chemicals, heat/cold…
 Keratinized vs. non-keratinized
 Location ? Where we need protection!
Skin surface
Entrances/exits of body, e.g. mouth, vagina

16. Nonkeratinized (noncornified)
stratified squamous epithelium

17. Keratinized (cornified) stratified
squamous epithelium
Thick
skin

18. Stratified cuboidal and stratified columnar:
quite rare, found in glands and ducts
Sweat gland

19. Transitional Epithelium
 Function ?
Extreme expansion & recoil
 Layered appearance due to overcrowding.
All cells contact BM.
 Location ?
 Bladder, ureters, renal pelvis

20. stretched

21. Bladder

22. Glandular Epithelia
Types of Glandular Secretions:
 Exocrine  Endocrine
 Glands have ducts  Glands have no
 Secretion to the ducts
“outside” of the body  Hormones (into
 Simple or compound the bloodstream)